This invention relates to an elevator control system.
In general, for improving the riding comfort of passengers in the elevator car and possibly eliminating errors in stopping the car at a desired target floor level, it is necessary not only to provide for adequate speed control but also to accurately detect the current car position. It may be contemplated that the driving motor speed control may be made based on a deceleration command signal corresponding to the remaining distance between the current car position and the target floor level thereby reducing level gap errors between the car level and the floor level.
So far, in detecting the current car position and computing the remaining distance to the target floor level, it is known in the art to use a floor memory consisting of a read-only memory for storing numbers corresponding to the floor positions in a binary format, and a current position counter, which is designed to compute the current car position based on the pulsed output of a tachometer generator coupled to a car being driven by an electric motor and to produce an output corresponding to the current car position similarly in the binary format. The floor positions as specified in the building are stored in the floor memory.
However, due to building errors or contraction of the building materials with the lapse of time, a certain gap, however small, is likely to occur between the actual and specified floor levels or positions. The result is that a gap or difference occurs between the car floor and the hall floor levels. In addition, any mounting error is translated directly into a corresponding constant level gap. This level gap may be reduced by providing suitable control points in the shaft for controlling the car position at these points. However, in this case, investment costs may be elevated due to provision of special devices. In addition, riding comfort may be affected by such frequent adjustment of the car positions.
Although the control system designed to obviate this inconvenience has already been proposed by the present applicant, it is not possible with this prior-art system to realize high control precision because the car is likely to surpass the target floor level during an initial period where the actual floor-to-floor distance is less than that specified in the building schedule. In addition, this prior-art system tends to be rather costly.